Use of oxygen absorbing substances for making flexible tubes

ABSTRACT

A metal tube for storing and distributing liquids, the tubes typically being manufactured of an aluminum alloy, comprising a cylindrical or truncated skirt having one end and another end linked to a dispensing head, the inner surface of the cylindrical skirt being covered, proximate to the open end, with an adhesive annular seal; and wherein the adhesive seal comprises an oxygen absorbing agent that is released when the tube is finally sealed; and wherein the oxygen absorbing agent is directly incorporated in the resin used for producing the seal to ensure that the oxygen absorbing agent is released only when the tube is finally sealed.

TECHNICAL FIELD

[0001] The invention relates to metallic receptacles such as aluminiumalloy tubes designed for storage and distribution of liquid to pastyproducts. These tubes form an excellent barrier to gas diffusion and areparticularly suitable for containing products sensitive to oxidation.

DESCRIPTION OF RELATED ART

[0002] Aluminium alloy tubes are obtained by impact extrusion of a slug.They comprise a cylindrical or truncated skirt with one open end and oneend connected to a dispensing head. The said dispensing head or collarcomprises a distribution neck generally delimiting an orifice that hasnot yet been opened and a shoulder connecting the neck to the skirt. Theinner surface of the tube is covered by a varnish and an annular sealnear the open end composed of a “latex based” resin, typically anadhesive resin based on synthetic rubber or an acrylic type resin, thesaid resins being in suspension in an aqueous solution.

[0003] Once made, the tubes are packaged upside down with the orificesealed and/or closed off by a cap and then sent to the packager. Thepackager fills them by delivering the product to be packaged through theopen end. When filling is complete, the portion of the skirt close tothe open end fitted with the annular seal is flattened along a diametersuch that the parts of the wall facing each other can come into contactover their entire surface and be adjacent to each other. This flattenedend is then folded over itself several times (usually 2 or 3 folds aremade) and then compressed. Consequently, due to the adhesive sealtrapped in the folds thus formed, the tube containing the product isfinally sealed so as to make the said tube leak tight. The seal isself-adhesive or thermo-adhesive depending on the material used.

[0004] Until recently, this type of practice was fully satisfactorybecause the essential requirement was leak tightness to liquids toprevent a product contained in the tube from leaking. At the moment,aluminium alloy tubes are less frequently used for packaging productsfor daily consumption (such as toothpaste), but they are stillparticularly in demand for packaging products sensitive to degradationby ambient air, and particularly easily oxidisable products. Thus,cosmetics for which the invention is applicable include hair dyes andanti-aging creams, containing products such as retinol or vitamin C.

[0005] Formulations offered by cosmetics manufacturers are changing:they are becoming more and more efficient but they are also becomingmore and more sensitive to oxidation. Under the conditions describedabove, the seal is perfectly satisfactory for leak tightnessrequirements for liquids, but not for more severe gas tightnessrequirements, particularly for oxygen. Therefore, it is found that thefinal sealing of the tube described above is no longer sufficient topreserve the packaged product, since the product is immediately oxidisedby oxygen in the air trapped when the tube is being sealed or graduallyoxidised by air that diffuses through the adhesive seal.

STATEMENT OF THE PROBLEM TO BE SOLVED

[0006] Therefore, the Applicant attempted to solve the problems thatarise due to the appearance of these new products particularly sensitiveto oxidation.

PURPOSE OF THE INVENTION

[0007] The purpose of the invention is a metal tube comprising acylindrical or truncated skirt having one open end and another endconnected to a dispensing head, the inner surface of the saidcylindrical skirt being covered with an adhesive annular seal close tothe said open end, characterised in that the said adhesive sealcomprises an oxygen absorbing agent that is released when the tube isfinally sealed.

[0008] The tube is metallic because its wall has an excellent barrierproperty to oxygen diffusion, significantly better than is possible witha wall made of a polymer material. Preferably, this tube will be analuminium alloy, for practical shaping reasons. The Applicant has foundthat it is advantageous to release an oxygen absorbing agent previouslycontained in the seal close to the said pocket, to absorb oxygencontained in the residual air pocket remaining in contact with theproduct after the tube is sealed.

[0009] In order to be released only at the time of the final seal, theoxygen absorbing agent may be incorporated directly into the “latexbased” resin from which the seal is made, in the form of a chemical thatremains passive until it is brought into contact with the product to bepackaged. For example, products like those described in U.S. Pat. No.4,536,409 & U.S. Pat. No. 4,702,966 can be incorporated, which becomereducing after reaction with water contained in the product with whichthey come into contact due to their sensitivity to humidity.

[0010] The oxygen absorbing agent can also be simply included in anenvelope, or preferably in a large number of microcapsules incorporatedin the said “latex based” resin used to make the seal, this envelope orthese microcapsules being destroyed after the tube is filled and/orfinally sealed.

[0011] The oxygen absorbing agent is packaged inside the microcapsulesand is easy to mix in a liquid resin such as the resin used to make theseal. The microcapsules are simply incorporated and mixed in thisaqueous suspension, then the said “latex based” resin is deposited onthe internal wall of the tube when it is still in the liquid form. Ingeneral, this wall is already covered with a layer of varnish, usually aphenol epoxy type varnish. The “latex based” resin may possibly be driedat ambient temperature (self-adhesive seal) or at a high temperature(thermal adhesive seal). The microballs remain trapped in the hardenedseal after drying.

[0012] These microcapsules may be destroyed mechanically, takingadvantage of the operations necessary for the final seal (compressionand then folding of the edges of the open end, compression of the finalseal, etc). The envelope of these microcapsules can also be destroyed(or made permeable to oxygen) for example using a different type ofmechanical action (for example ultrasound) or by adding external energy(addition of heat, electromagnetic radiation such as microwaves,ultraviolet or infrared radiation) or by a chemical method (addition ofa solvent, water, lipids, pH of the packaged product, etc.).

[0013] The substance released during final sealing absorbs residualoxygen in the air pocket trapped in the receptacle after filling withthe product to be packaged and after closing the said receptacle.Preferably, this substance is provided in a sufficiently large quantityso that it can also absorb any oxygen that diffuses through theinterface between the flattened, glued or folded parts of the seal whilethe product is being used.

[0014] This substance is chosen as a function of usage conditions of theproduct packaged in the tube. It may be any oxidisable compoundcompatible with use of the product to be distributed such as ironpowder, a metallic salt such as a ferrous salt or a cobalt salt, anoxidisable compound chosen from the group containing reduced forms ofquinone, or an oxidisable composition comprising an active oxygenabsorbing compound chosen from among the group containing organicanti-oxidants, phosphites, phosphines and organic phosphates,hydroquinone, substituted hydroquinone, sulphates, sulphites, phosphitesand metal nitrites, thiodipropinoic acid and its esters and salts,thio-bis (ethylene glycol beta-aminocrotonate), cysteine, cystine,methionine, primary, secondary and tertiary amines and derivatives ofthem.

[0015] The diameter of the microcapsules varies between 1 and 50 μm.Depending on the nature of the oxygen absorbing agent, the envelopes aremade by drying, spray cooling, prilling), are coated with moltenpolymers, gelified polymers, hydrosoluble polymers in a fluidised bed,by phase separation (simple or complex coacervation), by solventelimination, polymerisation, cross linking, polycondensation, etc.

[0016] Depending on their composition, microcapsule envelopes may behydro or liposoluble with various natures of polymers such as agar,alginate, wax, collagen, polylactate, polyglycolate, gelatine,chitosane, ethyl-cellulose, carboxymethyl-cellulose, polysaccharide,polyvinyl alcohol, polyethylene-imine, vinyl acetate and mixes thereof.

1. Metallic tube comprising a cylindrical or truncated skirt with oneopen end and one end connected to a dispensing head, the inner surfaceof the said cylindrical skirt being covered by an annular adhesive sealnear the said open end, characterised in that the said adhesive sealcomprises an oxygen absorbing agent that is released when the tube isfinally sealed.
 2. Tube according to claim 1, in which the oxygenabsorbing agent is incorporated directly into the resin used to make theadhesive seal, in the form of a chemical that remains passive until itis brought into contact with the product to be packaged.
 3. Tubeaccording to claim 1, in which the oxygen absorbing agent is included inat least one envelope incorporated in the resin used to make the saidadhesive seal.
 4. Tube according to claim 3, in which the oxygenabsorbing agent is included in microcapsules with diameter varyingbetween 1 and 50 μm, and incorporated in the resin used to make the saidadhesive seal.
 5. Tube according to claim 3, in which the envelope isselected from capsules capable of being destroyed mechanically duringfinal sealing, by compression and then folding of the edges of the openend of the skirt.
 6. Tube according to claim 3, in which the envelope isselected from capsules capable of being destroyed using ultrasound. 7.Tube according to claim 3, in which the envelope is selected fromcapsules capable of being destroyed or made permeable to oxygen byadding external energy, such as heat, electromagnetic radiation such asmicrowaves, ultraviolet or infrared radiation.
 8. Tube according toclaim 3, in which the envelope is selected from capsules capable ofbeing destroyed or made permeable to oxygen by a chemical method, suchas addition of a solvent, water, lipids, modification due to the pH ofthe packaged product.
 9. Tube according to claim 1, in which the saidsubstance absorbing the oxygen is provided in a sufficiently largequantity so that it can also absorb any oxygen that diffuses through theinterface between the flattened, glued or folded parts of the seal whilethe product is being used.
 10. Tube according to claim 1, in which thesaid substance absorbing the oxygen belongs to the group containing ironpowder, metallic salts such as a ferrous salt or a cobalt salt,oxidisable compounds chosen from the group containing reduced forms ofquinone, or oxidisable compositions comprising an active oxygenabsorbing compound chosen from among the group containing organicanti-oxidants, phosphites, phosphines and organic phosphates,hydroquinone, substituted hydroquinone, sulphates, sulphites, phosphitesand metal nitrites, thiodipropinoic acid and its esters and salts,thio-bis (ethylene glycol beta-aminocrotonate), cysteine, cystine,methionine, primary, secondary and tertiary amines and derivativesthereof.
 11. Tube according to claim 3, in which the envelope is made ofa material belonging to the group containing agar, alginate, wax,collagen, polylactate, polyglycolate, gelatine, chitosane,ethyl-cellulose, carboxymethyl-cellulose, polysaccharide, polyvinylalcohol, polyethylene-imine, vinyl acetate and mixes thereof.
 12. Tubeaccording to claim 4, in which the microcapsules are selected fromcapsules capable of being destroyed mechanically during final sealing,by compression and then folding of the edges of the open end of theskirt.
 13. Tube according to claim 4, in which the microcapsules areselected from capsules capable of being destroyed using ultrasound. 14.Tube according to claim 4, in which the microcapsules are selected fromcapsules capable of being destroyed or made permeable to oxygen byadding external energy, such as heat, electromagnetic radiation such asmicrowaves, ultraviolet or infrared radiation.
 15. Tube according toclaim 4, in which the microcapsules are selected from capsules capableof being destroyed or made permeable to oxygen by a chemical method,such as addition of a solvent, water, lipids, modification due to the pHof the packaged product.
 16. Tube according to claim 4, in which themicrocapsules are made of a material belonging to the group containingagar, alginate, wax, collagen, polylactate, polyglycolate, gelatine,chitosane, ethyl-cellulose, carboxymethyl-cellulose, polysaccharide,polyvinyl alcohol, polyethylene-imine, vinyl acetate and mixes thereof.